The present invention relates to sprinklers and more specifically pertains to an improved turbine design for regulating the rotation speed of the sprinkler.
Sprinkler systems for turf irrigation are well known. Typical systems include a plurality of valves and sprinkler heads in fluid communication with a water source, and a centralized controller connected to the water valves. At appropriate times the controller opens the normally closed valves to allow water to flow from the water source to the sprinkler heads. Water then issues from the sprinkler heads in a predetermined fashion.
There are many different types of sprinkler heads, including above-the-ground heads and “pop-up” heads. Pop-up sprinklers, though generally more complicated and expensive than other types of sprinklers, are typically thought to be superior. There are several reasons for this. For example, a pop-up sprinkler's nozzle opening is typically covered when the sprinkler is not in use and is therefore less likely to be partially or completely plugged by debris or insects. Also, when not being used, a pop-up sprinkler is entirely below the surface and thus generally less obtrusive to the landscape.
The typical pop-up sprinkler head includes a stationary body and a “riser” which extends vertically upward, or “pops up” when water is allowed to flow to the sprinkler. Typically, the riser is a hollow tube which supports a nozzle at its upper end. When the normally-closed valve associated with a sprinkler opens to allow water to flow to the sprinkler, two things happen: (i) water pressure pushes against the riser to move it from its retracted to its fully extended position, and (ii) water flows axially upward through the riser, and the nozzle receives the axial flow from the riser and turns it radially to create a radial stream. A spring or other type of resilient element is interposed between the body and the riser to continuously urge the riser toward its retracted, subsurface, position, so that when water pressure is removed, the riser will immediately proceed from its extended to its retracted position.
The riser of a pop-up or above-the-ground sprinkler head can remain rotationally stationary or can include a portion that rotates in continuous or oscillatory fashion to water a circular or partly circular area, respectively. More specifically, the riser of the typical rotary sprinkler includes a first portion, which does not rotate, and a second portion, which rotates relative to the first (non-rotating) portion.
The rotating portion of a rotary sprinkler riser typically carries a nozzle at its uppermost end. The nozzle throws at least one water stream outwardly to one side of the nozzle assembly. As the nozzle assembly rotates, the water stream travels or sweeps over the ground.
The non-rotating portion of a rotary sprinkler riser typically includes a drive mechanism for rotating the nozzle. The drive mechanism generally includes a turbine and a transmission. The turbine is usually made with a series of angular vanes on a central rotating shaft that is actuated by a flow of fluid subject to pressure. The transmission consists of a reduction gear train that converts rotation of the turbine to rotation of the nozzle assembly at a speed slower than the speed of rotation of the turbine.
During use, as the initial inrush and pressurization of water enters the riser, it strikes against the vanes of the turbine causing rotation of the turbine and, in particular, the turbine shaft. Rotation of the turbine shaft, which extends into the drive housing, drives the reduction gear train that causes rotation of an output shaft located at the other end of the drive housing. Because the output shaft is attached to the nozzle assembly, the nozzle assembly is thereby rotated, but at a reduced speed that is determined by the amount of the reduction provided by the reduction gear train. An example of a nozzle assembly having this design can be seen in U.S. Pat. No. 4,681,260, which is herein incorporated by reference in its entirety.
With such sprinkler systems, a wide variation in fluid flow out of the nozzle can be obtained. If the system is subject to an increase in fluid flow rate through the riser, the speed of nozzle rotation increases proportionally due to the increased water velocity directed at the vanes of the turbine. In general, increases or decreases in nozzle speed then, of course, affect the desired water distribution.
Prior art sprinklers attempt to regulate the turbine speed by providing two water paths, one path leading to the turbine and another path bypassing the turbine. In typical designs of this type, pressure actuated valves divert a portion of the water around the turbine in an attempt to reduce the flow hitting the turbine, as seen in example U.S. Pat. Nos. 5,375,768 and 4,681,260, the contents of which are hereby incorporated by reference.
While the use of pressure actuated diversion valves within a sprinkler help regulate the water flow to the turbine, they become less than effective in extreme conditions, such as low flow or very high flow. For example, since such pressure valves only open at a certain pressure threshold such valves will not compensate for any fluctuations under that pressure threshold. In a similar manner, once the valve is completely open due to a relatively large water flow, such valves will not compensate for further fluctuations above a maximum pressure threshold.
Further, pressure activated valves can become maladjusted over time due to fatigue, wear, or even breakage. Replacement or repair of the valves can be difficult and costly.
As a result, there is a long felt need of a turbine rotation regulation device that is sensitive to changes in water flow pressure at any level, yet has an improved lifespan over prior designs.